Cleaning machines that operate by applying vacuum to a surface to be cleaned have long been known. An example can be found in U.S. Pat. No. 933,003 to Smith. The surface to be cleaned may be a carpeted surface or a hard surface such as hardwood or tile.
Surface cleaning machines that include a plurality of rotating suction inlets are also known. These types of machines generally include a rotating disk with suction inlets, which apply vacuum on an underlying surface through appropriately shaped openings such as round holes, slots, or combinations thereof. A cleaning liquid may be pre-applied to the surface before vacuuming or be sprayed by the cleaning machine, and the rotating suction inlets remove the used cleaning liquid and dirt particles through the combination of suction and scrubbing provided by the rotating disk. Examples of these types of machines can be found in U.S. Pat. No. 3,624,668 to Krause and U.S. Pat. Nos. 4,264,999, 4,339,840 and 8,453,293 to Monson.
One drawback of rotary cleaning machines in the prior art is that they provide for an inefficient cleaning of irregular surfaces. For example, a floor may not be perfectly flat but may have high and low points, such as ridges or channels. In those instances, the suction inlets may be lifted upward when the rotating disk encounters a high point and roll over at least a portion of that high point, failing to retain contact with the floor in the area surrounding the high point. Conversely, the rotating disk may bridge over a low point and the suction inlets may fail to penetrate therein. In either case, the cleaning efficiencies of such prior art machines are low when irregularities are present in the surface to be cleaned.
U.S. Pat. No. 4,441,229 to Monson attempts to solve the problem of cleaning irregular surfaces by disclosing a rotary cleaning machine, in which a hub member is longitudinally coupled to a star-shaped structure. Suction shoes are attached to the arms of the star-shaped structure and can move upward and downward due to the flexing of those arms.
A drawback of this solution is that the arms of the star-shaped structure may move upward and downward only to a limited degree, because those arms must have a sufficient thickness to support the weight of the machine at the suction shoes and maintain a positive pressure on the suction shoes.
Another drawback of this solution is that the star-shaped structure is generally made of metal and, therefore, is prone to fatigue, especially at the junction points where the arms of the star-shaped structure meet the central hub.
U.S. patent application publication No. 2012/0233804 to Studebaker et al. also attempts to solve the problem of cleaning irregular surfaces by disclosing a rotary cleaning machine, in which suction shoes protrude from a rotary disk. Resilient biasing means, such as closed foam rubber cushions, are positioned between the rears of the suction shoes and the rotary disk, enabling the suction shoes to float individually relative to the rotary disk.
Even in this case, however, the suction shoes can have only limited upward and downward mobility due to constraints in the possible thickness and density of the rubber cushions.